Damping system for steering wheel

ABSTRACT

A damping system includes: a fixed member; an airbag device including a back holder and disposed on a rear side of the fixed member; an elastic member mounted in a mounting hole of the back holder; and a horn switch mechanism including a support member supported on the fixed member on a front side of the back holder, and a slider disposed between the support member and the elastic member. The airbag device functions as a damper mass of a dynamic damper, and the elastic member functions as a spring thereof. The horn switch mechanism includes an extended portion extending forwards. An engaged portion is formed at a circumferential edge portion of the mounting hole to extend rearwards. The elastic member includes an engaging portion opened in a front surface thereof. The elastic member is sandwiched by the engaged portion fitted in the engaging portion and the extended portion.

BACKGROUND

1. Technical Field

The present invention relates to a damping system for suppressing(controlling) vibrations of a steering wheel which incorporates anairbag device.

2. Background Art

When vibrations are transmitted to a steering wheel in a verticaldirection and a horizontal direction while the vehicle is being drivenat high speed or an in-vehicle engine is idling, the comfortable drivingof the driver may be deteriorated. For this reason, techniques forsuppressing (controlling) the vibrations of a steering wheel have beendeveloped and proposed. One of the techniques employs a dynamic damperincluding a damper mass and an elastic member which supports the dampermass on a metallic core frame of the steering wheel. According to thistechnique, when vibrations of a frequency which is the same as or closeto a resonance frequency specific to the dynamic damper are transmittedfrom the steering wheel to the dynamic damper, the dynamic damperresonates to absorb the vibration energy of the steering wheel. Thevibration of the steering wheel is then suppressed (controlled) by theabsorption of the vibration energy.

Recently, the steering wheel incorporates therein an airbag device so asto protect the driver from impact produced when the vehicle is involvedin a collision. The airbag device includes an airbag and an inflator forsupplying a gas to the airbag. When the vehicle is involved in acollision, the airbag is inflated to the rear by supplying the gas intothe airbag, whereby the driver is protected from the impact producedupon collision.

The airbag device occupies most of an interior space defined within thesteering wheel. Therefore, in recent steering wheels, it becomesdifficult to incorporate the dynamic damper in the steering wheel.

Patent Document 1 describes a steering wheel in which an airbag deviceis made to double as a dynamic damper.

This steering wheel includes a holder, an airbag module, an elastic bodyand a horn switch. The holder is fixed to a steering shaft which extendsin a front-right direction. The airbag device is configured by attachingan inflator and an airbag to a bracket individually and is disposed on arear side of the holder. The elastic body is formed into a ring shapeand is mounted in a mounting hole formed so as to penetrate the bracketin the front-rear direction. The horn switch includes an annular sliderwhich is disposed between a support member and the elastic member, and ahorn unit is activated by a forward movement of the slider which occursin association with a pressing operation of the airbag device.

Patent Document 2 also describes a similar damping system.

According to the steering wheel, the airbag device functions as a dampermass of a dynamic damper, and the elastic member functions as a springof the dynamic damper. When the steering wheel vibrates in directionssuch as vertical and horizontal directions perpendicular to the steeringshaft with a predetermined frequency, the elastic member vibratestogether with the airbag device in directions perpendicular to thesteering shaft while the elastic member is deformed elastically with aresonance frequency which is the same or close to the predeterminedfrequency, whereby the vibration energy of the steering wheel isabsorbed. Accordingly, the vibration of the steering wheel is suppressed(controlled) by the absorption of the vibration energy.

-   Patent Document 1: JP-A-2009-202859-   Patent Document 2: JP-U-2-38275

SUMMARY

In Patent Document 1, since the elastic body is mounted in the mountinghole in the bracket, the elastic body has an outside diameter largerthan a diameter of the mounting hole. Then, a circumferential edgeportion of the circular mounting hole in the bracket is forced into theelastic body in a radially inward direction from an outer side of theelastic member, that is, in a direction perpendicular to the steeringshaft from the outer side of the elastic body.

As the configuration described above, a considered configuration is thatan annular groove is provided on an outer circumferential surface of anelastic body along a full circumference thereof, and a circumferentialedge portion of a circular mounting hole in a bracket is fitted in theannular groove. In this case, in order that the elastic member having alarger outside diameter than the mounting hole is mounted in themounting hole, the circumferential edge portion of the circular mountinghole has to be fitted in the annular groove while the elastic body islargely elastically deformed. Therefore, the mounting work of theelastic member in the mounting hole becomes complex and troublesome.

In addition, in the configuration, it becomes difficult to mount theelastic member in the mounting hole without a gap between an innerbottom surface of the annular groove and an inner wall surface of thecircular mounting hole. When such a gap is produced, an airbag moduleand the elastic body do not vibrate as designed, which may not providethe intended vibration control effect. In particular, since thedirection in which the circular mounting hole is fitted in the annulargroove and the direction in which the damper mass (the airbag module)and the spring (the elastic body) of the dynamic damper vibrate toreduce vibrations are the same directions perpendicular to the steeringshaft, the above-described problem with the gap is likely to be occur.

The problem can also occur similarly in Patent Document 2 having theconfiguration similar to that of Patent Document 1.

The invention has been made in view of these circumstances, and anobject thereof is to provide a damping system for steering wheel whichcan mount an elastic member in a state of restricting the movementthereof by simple work.

In one aspect of the invention, a damping system for steering wheel,includes: a fixed member fixed to a steering shaft extending in afront-rear direction; an airbag device which includes a back holderprovided at a front portion thereof and which is disposed on a rear sideof the fixed member; an elastic member mounted in a mounting hole formedin the back holder so as to penetrate therethrough in a front-to-reardirection; and a horn switch mechanism including a support membersupported on the fixed member at a position on a front side of the backholder, and a slider disposed between the support member and the elasticmember so as to activate a horn unit by a forward movement of the sliderassociated with a pressing operation of the airbag device, wherein thedamping system allows the airbag device to function as a damper mass ofa dynamic damper, and allows the elastic member to function as a springof the dynamic damper, wherein the horn switch mechanism furtherincludes an extended portion extending forwards, wherein the back holderincludes an engaged portion extending rearwards and formed at acircumferential edge portion of the mounting hole, wherein the elasticmember includes an engaging portion including a recess portion opened ina front surface of the elastic member, and wherein the elastic member issandwiched by the engaged portion fitted in the engaging portion and theextended portion in the front-rear direction.

In the damping system for steering wheel which is configured in the waydescribed above, the airbag device functions as the damper mass of thedynamic damper, and the elastic member functions as the spring of thedynamic damper. Because of this, when the steering wheel vibrates with apredetermined frequency in a direction perpendicular to the steeringshaft, the elastic member vibrates together with the airbag device inthe direction perpendicular to the steering shaft (the airbag device andthe elastic member resonate) so as to absorb the vibration energy of thesteering shaft. By absorbing the vibration energy in this way, thevibration of the steering wheel is suppressed (controlled).

In addition, in the steering wheel, when the airbag device is pressed,the slider moves forwards on the support member which is supported onthe fixed member, whereby the horn unit is activated.

In the steering wheel, when the horn switch mechanism is mounted on theback holder of the airbag device via the elastic member, mounting workof the horn switch mechanism on the elastic member and mounting work ofthe elastic member in the mounting hole are performed.

When performing the former work, the horn switch mechanism is disposedat the rear of the elastic member so that the extended portion extendsforwards. By the horn switch mechanism being so disposed, the extendedportion is caused to face a rear surface of the elastic member. In thisstate, the slider of the horn switch mechanism is inserted through theelastic member. In association with this insertion of the slider, theextended portion of the horn switch mechanism approaches the elasticmember from a rear side thereof to thereby be brought into contact withthe rear surface of the elastic member.

When performing the latter work, the elastic member is disposed so thatthe engaging portion is oriented to the front at the rear of themounting hole in the back holder. By the elastic member being disposedin this way, the engaging portion of the elastic member is caused toface the engaged portion of the circumferential edge portion of themounting hole. When the elastic member is caused to approach themounting hole in this state, the engaged portion is fitted in theengaging portion.

In this way, the elastic member is sandwiched from front and rearthereof by the engaged portion and the extended portion. A movement ofthe elastic member in a direction which follows the steering shaft (thefront-rear direction) is restricted by the engaged portion and theextended portion. Additionally, a movement of the elastic member in adirection perpendicular to the steering shaft is restricted by theengaged portion which is fitted in the engaging portion.

As a result, the airbag device and the elastic member are allowed tovibrate as designed while facilitating the mounting work of the elasticmember, thereby making it possible to exhibit the vibration controllingeffect.

In the damping system for steering wheel according to theabove-described aspect, the elastic member may include a groove portionwhich is opened in at least one of the front surface and a rear surfaceof the elastic member.

According to the configuration described above, the groove portion whichis opened in at least one of the front surface and the rear surface ofthe elastic member facilitates the elastic deformation of the elasticmember. Because of this, when the steering wheel vibrates, the elasticmember is allowed to resonate easily together with the airbag device,whereby it becomes easier to obtain the suppressing (controlling) effectof the vibration of the steering wheel.

In the damping system for steering wheel according to theabove-described aspect, the groove portion may be formed between theengaging portion and the slider.

Here, when the steering wheel vibrates, it is considered that it is aportion between the engaging portion and the slider that is mainlydeformed in an elastic fashion in the elastic member.

In the third aspect, by forming the groove portion between the engagingportion and the slider, the portion in relation to the elasticdeformation is made to be elastically deformed more easily, whereby theeffect provided in the second aspect can be obtained more easily.

According to the damping system for steering wheel of the aspects of theinvention, the elastic member can be mounted while the movement thereofis restricted by performing the simple work.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show an embodiment of the invention, in which FIG. 1A isa side view of a steering wheel and FIG. 1B is a view of the steeringwheel as seen in a direction indicated by an arrow A.

FIG. 2 is a partial front view of a metallic core frame of the steeringwheel.

FIG. 3 is a perspective view of an airbag device showing a state of theairbag device as seen from a back side of the airbag device (a frontside of the vehicle).

FIG. 4 is an exploded perspective view showing a state in whichrespective constituent components of the airbag device are seen from theback side (the front side of the vehicle).

FIG. 5A shows an exploded perspective view of a horn switch mechanism,and FIG. 5B is a perspective view of a resin member showing a state inwhich the resin member is seen from the front side.

FIG. 6 is a partial front view showing a state in which the horn switchmechanism is assembled in one of mounting holes in a back holder.

FIG. 7 is a partial back view showing a state in which the horn switchmechanism is assembled in the one of the mounting holes in the backholder.

FIG. 8 is an enlarged sectional view taken along the line XX in FIG. 6.

FIG. 9 is a sectional view showing a state in which the horn switchmechanism shown in FIG. 8 is assembled to the back holder via an elasticmember.

FIG. 10 is an enlarged sectional view taken along the line Y-Y in FIG.6.

FIG. 11 is an enlarged sectional view taken along the line ZZ in FIG. 7.

FIG. 12 is a partially sectional view showing an internal structure ofthe horn switch mechanism which is mounted on the metallic core frame.

FIG. 13 is a partially sectional view showing an internal structure ofthe horn switch mechanism before it is mounted on the metallic coreframe.

FIG. 14 is a partially sectional view showing an internal state of thehorn switch mechanism resulting when the airbag device is pressed.

DETAILED DESCRIPTION

Hereinafter, referring to the drawings, an embodiment of the inventionwill be described in which the invention is embodied in a damping systemfor a steering wheel of a vehicle.

As shown in FIG. 1A, a steering shaft 14 which extends along an axis L1in a front-rear and which rotates about the axis L1 is mounted in aposition in a vehicle which lies further forwards (leftwards in FIG. 1A)than a driver's seat so as to be inclined so that an end (a right end inFIG. 1A) of the steering shaft which lies to face the driver's seat getshigher. A steering wheel 10 according to this embodiment is mounted at arear end portion of the steering shaft 14 so as to rotate together withthe steering shaft 14.

In this embodiment, when describing them, constituent portions of thesteering wheel 10 will be described based on the axis L1 of the steeringshaft 14. A direction which follows the axis L1 is referred to as a“front-rear,” and in directions perpendicular to the axis L1, adirection in which the steering wheel 10 is erected is referred to as“vertical direction.” Consequently, it follows that the front-reardirection and the vertical direction of the steering wheel 10 areslightly inclined relative to a front-rear (a horizontal direction) anda vertical direction (a perpendicular direction) of the vehicle.

It should be noted that in FIGS. 12 to 14, as a matter of convenience,the front-rear direction of the steering wheel 10 is shown as coincidingwith the horizontal direction and the vertical direction of the steeringwheel 10 is shown as coinciding with the perpendicular direction.

As shown in FIG. 1B, the steering wheel 10 includes an airbag device (anairbag module) 20 in a central portion thereof. A frame portion of thesteering wheel 10 is made up of a metallic core frame 12 as a fixedmember. FIG. 2 shows part of the metallic core frame 12. The metalliccore frame 12 is formed of iron, aluminum, magnesium or alloys thereof.The metallic core frame 12 is fixed to the steering shaft 14 at a bossportion 12a which is positioned at a central portion thereof and rotatestogether with the steering shaft 14.

In the metallic core frame 12, holding portions 12b having a throughhole 12c are provided at a plurality of locations (three locations inthis embodiment) along the periphery of the boss portion 12. In themetallic core flame 12, when it is necessary to distinguish the holdingportions 12b from the remaining portion, the latter portion will bereferred to as a metallic core frame main body 12i. As shown in FIG. 13,an inner wall surface of each through hole 12c is tapered so that anopening defined by the inner wall is expanded diametrically as thethrough hole 12c extends towards the rear (the left as seen in FIG. 13).In FIG. 2, the illustration of this tapered inner circumferentialsurface is omitted.

As shown in FIGS. 2 and 13, a clip 13 is built in between each holdingportion 12b and the metallic core frame main body 12i and near thethrough hole 12c. Each clip 13 is formed by bending a wire material madeof a metal such as a spring steel into a predetermined shape and isbuilt in between the holding portion 12b and the metallic core framemain body 12i while being slightly deformed in an elastic fashion so asto be held onto the metallic core frame 12. The clip 13 is brought intocontact with at least one of the holding portion 12b and the metalliccore frame main body 12i at part or an end portion thereof, for example.The clip 13 has a function to lock a fixing pin 31 of a horn switchmechanism 15, which will be described later, relative to the metalliccore frame 12 while establishing an electric communication therebetween.Part of each clip 13 is positioned near the front of the through hole12c.

A horn unit 40 (refer to FIG. 13) is provided in the vehicle, and aplurality of (three in this embodiment) horn switch mechanisms 15 aremounted individually in the holding portions 12b using a snap-in fittingstructure so as to activate the horn unit 40. The respective horn switchmechanisms 15 have the same configuration. Then, the airbag device 20 issupported on the metallic core frame 12 via these horn switch mechanisms15, in this way, each born switch mechanism 15 doubles as a support forthe airbag device 20 in addition to its function as the horn switch.

Further, in this embodiment, an elastic member 42 is interposed betweenthe airbag device 20 and each horn switch mechanism 15, and a dampingsystem for suppressing (controlling) vibrations of the steering wheel 10is made up of the airbag device 20 and the elastic members 42.

Next, the airbag device 20, each horn switch mechanism 15 and eachelastic member 42 will be described individually.

<Airbag Device 20>

As has been described above, the airbag device 20 is part of the dampingsystem of the steering wheel 10 and is, as shown in FIGS. 3 and 4, madeup by assembling a pad portion 24, an airbag (not shown) and an inflator23 to a back holder 21 which is disposed at a front portion of theairbag device 20. This airbag device 20 is disposed at a rear side ofthe metallic core frame 12.

The pad portion 24 is made through resin molding and has a skin portion24a whose surface is finished into a designed surface, an accommodationwall portion 24b which is erected into a substantially quadrangular ringshape on a rear surface side (a front side: a right-hand side as seen inFIGS. 3 and 4) of the skin portion 24a. An inner surface of the skinportion 24a which is surrounded by the accommodation wall portion 24bdefines a bag accommodation space X (refer to FIG. 4) for accommodatingmainly the airbag (not shown) between the back holder 21 and itself. Athin portion 24c, which is adapted to be pushed to be broken when theair bag is deployed and inflated, is formed at a portion of the skinportion 24a where the bag accommodation space X is defined.

A plurality of (six) locking claws 24d having a rectangular plate-likeshape are formed integrally at a front end portion (a right end portionin FIG. 4) of the accommodation wall portion 24b. Each locking claw 24dis formed wide with a predetermined length, and a locking projection 24e(refer to FIG. 3) which projects outwards (a side which lies fartherfrom the bag accommodation space X) is formed at a front end portion ofeach locking claw 24d.

Switch supporting portions 24g, which are adapted to support thecorresponding horn switch mechanisms 15, are formed individually at aplurality of locations (three locations) on the pad portion 24. Eachswitch supporting portion 24g is formed integrally with theaccommodation wall portion 24b so as to extend from the skin portion 24aof the pad portion 24 towards the rear surface side (the front side).

As shown in FIGS. 3, 4, 6 and 7, the back holder 21 is formed into asubstantially rectangular shape by pressing a metal plate. Additionally,the back holder 21 may be formed through die casting. A circumferentialedge portion of the back holder 21 is configured into a substantiallyquadrangular ring-shaped circumferential edge fixing portion 21a towhich the pad portion 24 is fixed.

Claw locking holes 21b are formed individually in the circumferentialedge fixing portion 21a at locations (front locations) which correspondto the clocking claws 24d of the pad portion 24. Each claw locking hole21b is formed into a slit which is elongated in a direction whichfollows a side of the back holder 21 so as to correspond to each widelocking claw 24d. A front end portion of each locking claw 24d isinserted through each claw locking hole 21b so as to be locked therein.

An internal portion defined within the circumferential edge fixingportion 21a makes up a substantially square seat portion 21f. A circularopening portion 21g is formed in a central portion of the seat portion21f. Screw insertion holes 21h are formed in the seat portion 21f at aplurality of locations near a circumferential edge portion of theopening portion 21g, here, at locations, four in total, which arelocated on diagonals of the seat portion 21f. The inflator 23 is mountedon the seat portion 21f with part thereof inserted through the openingportion 21g in the seat portion 21f.

More specifically, the inflator 23 has low cylindrical main body, and aflange portion 23a is formed on an outer circumferential surface of themain body. A plurality of (or four) mounting pieces 23b are formed onthe flange portion 23a at equal angular intervals in a circumferentialdirection of the main body so as to extend radially outwards of the mainbody. In each mounting piece 23b, a screw insertion hole 23c is formedat a location (a front location) which corresponds to the screw throughhole 21h in the back holder 21, in the inflator 23, a portion which liesfurther rearwards than the flange portion 23a is configured as a gasinjection portion 23x (refer to FIG. 4) from which an inflation gas isinjected. Then, the gas injection portion 23x of the inflator 23 isinserted through the opening portion 21g in the back holder 21 from thefront side so as to project towards the bag accommodation space X side.Further, the flange portion 23a is brought into abutment with thecircumferential edge portion of the opening portion 21g, and in thisstate, the inflator 23 is mounted on the back holder 21 together with aring retainer 25 (refer to FIG. 4).

To describe in greater detail, the ring retainer 25 has a circularopening portion 25a which is similar to the opening portion 21g in theback holder 21 through which the gas injection portion 23x of theinflator 23 is inserted. Additionally, the ring retainer 25 has mountingscrews 25b at a plurality of locations (four locations) which correspondto the screw through holes 21h in the back holder 21. An opening portionof an airbag (not shown) which is folded so as to be deployed andinflated is disposed between the ring retainer 25 and the back holder21. The plurality of mounting screws 25b of the ring retainer 25 areinserted through screw insertion holes which are provided in acircumferential edge portion of the opening portion of the airbag andthe screw insertion holes 21h, 23c of the back holder 21 and theinflator 23, respectively, from the rear side. Further, nuts 26 arescrewed on the mounting screws 25b that have been inserted through therespective screw insertion holes from the front side, whereby the airbagis fixed to the back holder 21 via the ring retainer 25, and theinflator 23 is fixed to the back holder 21.

Mounting portions 21d in which the horn switch mechanisms 15 are mountedare formed at a plurality of locations (three locations) along thecircumferential edge fixing portion 21a of the back holder 21 so as toproject individually radially outwards of the circular opening portion21g. The respective mounting portions 21d are situated at locations(front locations) which correspond to the switch supporting portions 24gof the pad portion 24. A mounting hole 21e in which the horn switchmechanism 15 is mounted is formed in each mounting portion 21dcircularly and so as to penetrate the mounting portion 21d. A pluralityof engaged portions 21j which extends rearwards individually are formedintegrally on a circumferential edge portion of each mounting hole 21ein the back holder 21 (refer to FIG. 9). In this embodiment, eachengaged portion 21j is formed by bending the circumferential edgeportion of each mounting hole 21e in the back holder 21.

<Horn Switch Mechanism 15>

The horn switch mechanisms 15 are such as to activate the horn unit 40as has been described above, and three horn switch mechanisms 15 areused in this embodiment. It is desired that the horn switch mechanisms15 are set individually equidistant from the center (the boss portion12a) of the steering wheel 10. This is because a contact terminal 34 anda collar portion 31a of a fixing pin 31, which will both be describedlater, are brought into contact with each other in an ensured fashion toproduce an electrically communicating state therebetween.

As shown in FIG. 5A, each horn switching mechanism 15 includes ametallic fixing pin 31 which functions as a support member and a fixedside contact portion, a movable mount member 32 as a slider, a capmember 33 made of a resin, a contact terminal 34 as a movable sidecontact portion, a resin member 41 and a coil spring 35 as a biasingmember. Next, the respective constituent members of the horn switchmechanism 15 will be described.

The fixing pin 31 is a member that is supported on the metallic coreframe 12 in a position on a front side of the back holder 21. Asupporting structure will be described later in which the fixing pin 31is supported on the metallic core frame 12. The fixing pin 31 has a longshape and extends in the front-rear direction, and a recess portion isprovided on an outer circumferential surface of a front end portion (aright end portion in FIG. 5A). In this embodiment, as the recessportion, an annular locking groove 31b is formed along the fullcircumference of the fixing pin 31. Most of the fixing pin 31 excludinga rear end portion is formed slightly smaller in diameter than themounting hole 21e (refer to FIG. 4) in the back holder 21. A collarportion 31a which is larger in diameter than the mounting hole 21e isformed at the rear end portion of the fixing pin 31 diameter of thecollar portion 31a of each pin 31 is set to be larger than a diameter ofthe corresponding shaft portion of the pin 31. The collar portion 31a isa portion which functions as the fixed side contact portion.

The movable mount member 32 is formed of a material having acharacteristic as an insulator, for example, a resin material. Thismovable mount member 32 has a stepped cylindrical shape and is disposedbetween the fixing pin 31 and the elastic member 42, which will bedescribed later. In activating the horn switch mechanism 15, the movablemount member 32 is used as a slider which slides in the longitudinaldirection (the front-rear direction). In the movable mount member 32, afitting portion 32b into which the collar portion 31a of the fixing pin31 is fitted is formed at a rear end of a portion through which thefixing pin 31 is inserted (hereinafter, referred to as a “cylindricalportion 32a”). The fitting portion 32b is brought into abutment with afront surface and an outer circumferential surface of the collar portion31a of the fixing pin 31 on an inner circumferential surface thereof.Additionally, projecting abutment portions 32g are provided at twolocations on the fitting portion 32b which face each other in adiametrical direction so as to project in a radial direction.

As shown in FIG. 5A and FIG. 11, locking portions 32e extend forwardsfrom a plurality of locations (four locations) along a circumferentialdirection on a front surface of the fitting portion 32b. A gap is setbetween each locking portion 32e and the cylindrical portion 32a (referto FIG. 11), and each locking portion 32e can deflect in the radialdirection.

As shown in FIG. 5A and FIG. 8, the cap member 33 has a bottomedcylindrical shape which is opened at a front surface and is assembled tothe fitting portion 32b of the movable mount member 32 so as to coverthe fixing pin 31 and the movable mount member 32 from the rear. The capmember 33 has a substantially circular top plate portion 33a and asubstantially cylindrical side wall portion 33b which extends forwardsfrom an outer circumferential edge of the top plate portion 33a. Here,the side wall portion 33b makes up part of the horn switch mechanism 15and is used as an extended portion which is extended to the front. Asshown in FIG. 5A and FIG. 10, a pair of hook portions 33c are formed attwo locations on the side wail portion 33b which face each other in thediametrical direction so as to be deformed elastically in the radialdirection.

As shown in FIG. 5A and FIG. 8, a groove 33d is formed at a rear portionof the top plate portion 33a so as to align the orientation of the capmember 33 when the cap member 33 is assembled to the fixing pin 31 andthe movable mount member 32. As shown in FIG. 5A and FIG. 10, formingholes 33e which form undercut portions of the hook portions 33c areformed in the groove 33d in positions which correspond to the hookportions 33c. Then, the forming holes 33e are dosed by the projectingabutment portions 32g on the movable mount member 32 which is broughtinto abutment with the top plate portion 33a of the cap member 33.Because of this, the intrusion of foreign matters such as dust into aninterior of the cap member 33 from the respective forming holes 33e isprevented, whereby a problem with electrical communication between thefixing pin 31 and the contact terminal 34 is suppressed from beingcaused.

As shown in FIG. 5A and FIG. 8, the contact terminal 34 is formed bypressing a metallic plate. The contact terminal 34 includes an elongatedmain body portion 34a which extends in the diametrical direction of thecap member 33, a pair of first side portions 34b which extends forwardsfrom both ends of the main body portion 34a, and a pair of second sideportions 34c which are disposed further radially outwards and forwardsof the cap member 33 than both the first side portions 34b and which areconnected to front end portions of the first side portions 34b byconnecting portions 34d.

The main body portion 34a is brought into contact with a front surfaceof the top plate portion 33a, and each first side portion 34b is broughtinto contact with an inner wall surface of the side wall portion 33b ofthe cap member 33. Each connecting portion 34d is brought into contactwith a front end face of the side wall portion 33b, and each second sideportion 34c is situated further radially outwards than the side wailportion 33b.

A plurality of (three in this embodiment) projecting contact portions34e which project forwards are formed on the main body portion 34a atequal intervals along a longitudinal direction of the main body portion34a.

Additionally, the fitting portion 32b of the movable mount member 32 isinterposed between each first side portion 34b and the collar portion31a of the fixing pin 31 so as to ensure an insulation state betweeneach first side portion 34b and the collar portion 31a. In addition, thecylindrical portion 32a of the movable mount member 32 and the elasticmember 42 are interposed between each second side portion 34c and thefixing pin 31 so as to ensure an insulation state between each secondside portion 34c and the fixing pin 31.

As shown FIG. 5B and FIGS. 8 and 11, the resin member 41 is formedintegral of a synthetic resin which is an insulation material in whole.Part of this resin member 41 is made up of an annular ring-like portion41b having an insertion hole 41a which is slightly larger in diameterthan the fixing pin 31. An outside diameter of the ring-like portion 41bis set almost similar to an outside diameter of the coil spring 35 andan outside diameter at a rear end portion of the inner wall surface ofthe through hole 12c (a maximum diameter of the opening defined by thetapered inner wall surface).

Locking pieces 41c extend forwards from a plurality of locations (fourlocations) which lie near the insertion hole 41a in the front surface ofthe ring-like portion 41b and along a circumferential direction of theinsertion hole 41a. A claw portion 41d is provided at a front endportion of each locking piece 41c so as to project radially inwards, andthese claw portions 41d enter the interior of the locking groove 31b ofthe fixing pin 31. External surfaces of the locking pieces 41c make uppart of a cylindrical surface which has the same diameter at anylocations in the front-rear direction. Namely, the external surfaces ofthe locking pieces 41c do not correspond to the tapered inner wallsurface of the through hole 12c, and therefore, the external surfacesare not brought into surface contact with the inner wall surface.

Additionally, a plurality of (four) engaging pieces 41e extend forwardsfrom positions on a front surface of the ring-like portion 41b which liealong the circumference of the insertion hole 41a and between theadjacent locking pieces 41c. External surfaces of the engaging pieces41e make up part of a tapered surface which expands diametrically as itextends to the rear.

A pair of mounting portions 41g extend rearwards from the ring-likeportion 41b. Each mounting portion 41g is formed to be curved so as tobe protuberant radially outwards of the resin member 41 corresponding toan external shape of the fixing pin 31.

Then, the resin member 41 is made up of the ring-like portion 41b, thelocking pieces 41c, the engaging pieces 41e and both the mountingportions 41g.

This resin member 41 is fitted on an external side of the fixing pin 31at the ring-like portion 41b and both the mounting portions 41g and ismounted on the fixing pin 31 so as not to come off the fixing pin 31 bythe claw portions 41d entering the locking groove 31b. Thus, as has beendescribed above, in the resin member 41, the external surfaces of thefour engaging pieces 41e surround intermittently (in a discontinuousfashion) an axis which passes through the center of the ring-likeportion 41b while holding the external surfaces of the locking pieces41c therebetween in an alternate fashion. By adopting thisconfiguration, the resin member 41 has the external surface which issomething like a tapered external surface which expands diametrically asit extends to the rear.

As shown in FIG. 5A and FIG. 12, the coil spring 35 is wound around thefixing pin 31 except for the collar portion 31a. The coil spring 35 isdisposed between a step portion 32f formed to the cylindrical portion32a of the movable mount member 32 and the ring-like portion 41b of theresin member 41 so as to be compressed therebetween. In this state, thering-like portion 41b receives a forward biasing force of the compressedcoil spring 35.

In this way, the plurality of single components (the fixing pin 31, themovable mount member 32, the cap member 33, the contact terminal 34, thecoil spring 35 and the resin member 41) are unitized so as to make upthe horn switch mechanism 15 which is an assembly. Because of this, whenmounting or replacing the horn switch mechanism 15, the unitized hornswitch mechanism 15 can be handled as one assembly.

<Elastic Member 42>

As shown in FIGS. 8 and 9, the elastic member 42 is, as has beendescribed above, such as to make up part of the damping system for thesteering wheel 10 and is interposed between the movable mount member 32of the horn switch mechanism 15 and the mounting hole 21e in the backholder 21 of the airbag device 20. The elastic member 42 is formed of anelastic material such as rubber or elastomer in whole. An engagingportion 42a which is made up of an annular recess portion which isopened at a front surface thereof is provided on the elastic member 42.The engaging portion 42a is formed at a location (a rear location) whichcorresponds to the engaged portion 21j of the back holder 21. Theengaged portion 21j is fitted in this engaging portion 42a from thefront side. A portion of the elastic member 42 is disposed between theslider 32 and the engaged portion 21j and the mounting portion 21d ofthe back holder. A portion of a front surface 42f of the elastic memberabuts a rear surface of the mounting portion 21d. A front end 42g of theelastic member extends forward of the rear surface of the mountingportion 21d.

Further, as shown in FIG. 5A and FIG. 10, the elastic member 42 has aninsertion hole 42b which is slightly large in diameter than thecylindrical portion 32a of the movable mount member 32 and is formedinto a substantially annular shape. Stepped portions 42e are formed onan outer circumferential portion of the elastic member 42 at twolocations which face each other in a diametric direction.

Then, as shown in FIG. 11, in such a state that the fitting portion 32bis in abutment with a rear surface of the elastic member 42, part of afront end portion of the side wall portion 33b of each cap member 33 isin abutment with a rear surface of the elastic member 42. In this way,the elastic member 42 is sandwiched from front and rear by the engagedportion 21j of each mounting holes 21e in the hack holder 21 and theside wall portion 33b of each cap member 33. In addition, in this state,as shown in FIG. 8, the connecting portions 34d of each contact terminal34 are brought into abutment with the rear surface of the elastic member42, and the second side portions 34c are brought into abutment with anouter circumferential surface of the elastic member 42.

Further, as shown in FIG. 11, the plurality of locking portions 32e areinserted through the through hole 42b, and front end portions of thelocking portions 32e are locked on the front surface of the elasticmember 42 from a radially inward direction. In addition to this, asshown in FIG. 10, the two hook portions 33c of the cap member 33 arelocked on the corresponding stepped portions 42e of the elastic member42 from a radially outward direction of the elastic member. By thelocking portions 32e and the hook portions 33c being locked in the waydescribed above, the elastic member 42 is mounted so as not to move inthe front-rear direction relative to the movable mount member 32 and thecap member 33.

As shown in FIG. 9, an annular groove portion 42c is formed in theelastic member 42 which is opened at a front surface thereof. Similarly,an annular groove portion 42d is formed in the elastic member 42 whichis opened at a rear surface thereof. The groove portion 42c is situatedbetween the insertion hole 42b (the movable mount member 32) and theengaging portion 42a in the elastic member 42. The groove portion 42d issituated at a portion which lies at the rear of the groove portion 42cin the elastic member 42.

The elastic member 42 is such as to make up the dynamic damper togetherwith the airbag device 20 that has been described before. In thisembodiment, the elastic member 42 is caused to function as a spring ofthe dynamic damper 42, and the airbag device 20 is caused to function asa damper mass.

Here, by tuning the size, radial thickness and front-rear length of theelastic member 42, the resonance frequency of the dynamic damper in thevertical and horizontal directions is set to a designed vibrationcontrol frequency (a frequency with which vibrations are desired to becontrolled) with respect to vertical and horizontal vibrations of thesteering wheel 10.

Thus, the damping system for steering wheel of the embodiment isconfigured as has been described heretofore. Next, the function of theembodiment will be described, while focusing on the function of thedamping system.

Firstly, the mounting work will be described in which each hornswitching mechanism 15 is mounted on the back holder 21 of the airbagdevice 20 via the elastic member 42. As this work, work of mounting eachhorn switch mechanism 15 on the elastic member 42 and work of mountingthe elastic member 42 in the mounting hole 21e are performed.

As to the former work, as shown in FIG. 9, the horn switch mechanism 15is disposed at the rear (on the left in FIG. 9) of the elastic member 42so that the side wall portion 33b of the cap member 33 extends to thefront. By so disposing, the side wall portion 33b is caused to face therear surface of the elastic member 42. In this state, the horn switchmechanism 15 is inserted in the insertion hole 42b in the elastic member42 at the movable mount member 32. As the horn switch mechanism 15 isinserted in this way, the side wall portion 33b of the cap member 33approaches the elastic member 42 from the rear. The second side portions34c of the contact terminal 34 slide on the outer circumferentialsurface of the elastic member 42. As shown in FIG. 11, when the movablemount member 32 is inserted to a position where the fitting portion 32bis brought into abutment with the rear surface of the elastic member 42,part of the front end portion of the side wall portion 33b is broughtinto abutment with the rear surface of the elastic member 42.Additionally, as shown in FIG. 8, the connecting portions 34d of thecontact terminal 34 is brought into abutment with the rear surface ofthe elastic member 42, and both the second side portions 34c are broughtinto abutment with a rear surface of the back holder 21. By thisabutment, the back holder 21 and the contact terminal 34 are put into anelectrically communicating state.

Further, as shown in FIG. 11, as the movable mount member 32 is insertedthrough the insertion hole 42b, the plurality of locking portions 32eare inserted into the insertion hole 42b while being deflected radiallyinwards. When front end portions of the locking portions 32e passthrough the insertion hole 42b during this insertion of the lockingportions 32e, the locking portions 32e are locked on the front surfaceof the elastic member 42 from the radially inward direction by virtue oftheir own elastic restoring force, in addition to this, as shown in FIG.10, the two hook portions 33c of the cap member 33 are locked on thecorresponding stepped portions 42e of the elastic member 42 from theradially outward direction of the elastic member 42. By the lockingportions 32e and the hook portions 33c being locked in the waysdescribed above, the elastic member 42 is mounted on the movable mountmember 32 so as not to move in the front-rear direction with respect tothe movable mount member 32 and the cap member 33.

When performing the latter work, as shown in FIG. 9, the elastic member42 is disposed at the rear of the mounting hole 21e in the back holder21 so that the engaging portion 42a is oriented to the front. By theelastic member 42 being so disposed, the engaging portion 42a of theelastic member 42 is caused to face the engaged portion 21j at thecircumferential edge portion of the mounting hole 21e. When the elasticmember 42 is caused to approach the mounting hole 21e in this state, theengaged portion 21j is fitted into the engaging portion 42a from thefront side as shown in FIG. 8.

In this way, the elastic member 42 is sandwiched from front and rear bythe engaged portion 21j of the back holder 21 and the side wall portion33b of the cap member 33.

In such a state that the horn switch mechanisms 15 are mountedindividually on the back holder 21 in the way described above, themovement of the elastic member 42 in the direction along the axis L1 ofthe steering shaft 14 (in the front-rear direction) is restricted by theengaged portion 21j and the side wall portion 33b. Additionally, themovement of the elastic member 42 in the direction perpendicular to theaxis L1 of the steering shaft 14 is restricted by the engaged portion21j which is fitted in the engaging portion 42a.

In such a state that the horn switch mechanisms 15 are mounted on theback holder 21 in the way described above, the collar portion 31a of thefixing pin 31 is situated further rearwards than the back holder 21.This collar portion 31a receives a rearward biasing force from the coilspring 35.

In addition, in such a state that the horn switch mechanisms 15 aremounted on the back holder 21 in the way described above, the movablemount member 32 is interposed between the fixing pin 31 and the backholder 21 and supports the back holder 21 so as to move in thefront-rear direction relative to the fixing pin 31 while preventing thecontact of the fixing pin 31 with the back holder 21, that is, ensuringthe insulation state therebetween, transmitting the rearward biasingforce of the coil spring 35 to the collar portion 31a of the fixing pin31.

Additionally, in such a state that the horn switch mechanisms 15 aremounted on the back holder 21 in the way described above, the top plateportion 33a of the cap member 33 is brought into abutment with theswitch supporting portions 24g of the pad portion 24 that has beendescribed before (refer to FIG. 3). Thus, the dislocation of the capmember 33 from the movable mount member 32 is restricted by thisabutment. For example, even the dislocation of the cap member 33 fromthe movable mount member 32 is restricted that would otherwise be causedby a reaction force produced when the airbag device 20 is struckstrongly.

Further, in such a state that the horn switch mechanisms 15 are mountedon the back holder 21 in the way described above, the coil springs 35 ofthe horn switch mechanisms 15 and the fixing pins 31 which are insertedthrough the coil springs 35 project to the front (in the direction inwhich they move away from the pad portion 24) from the back holder 21.

Next, the mounting work of mounting the airbag device 20 on the metalliccore frame 12 via the plurality of (three) horn switch mechanisms 15will be described.

When performing this work, as shown in FIG. 13, each fixing pin 31 iscaused to approach the through hole 12c in each holding portion 12b ofthe metallic core frame 12 from the rear. As this occurs, a portion ofeach fixing pin 31 which lies further forwards than the locking groove31b (hereinafter, referred to as a “front end 31c”) project slightly tothe front from the coil spring 35 and the resin member 41.

The resin member 41 has already been mounted on the fixing pin 31 beforethe fixing pin 31 is inserted through the through hole 12c, andtherefore, the resin member 41 is also inserted into the through hole12c when the fixing pin 31 is inserted through the through hole 12c.

As the resin member 41 is inserted into the through hole 12c, thering-like portion 41b of the resin member 41 approaches the holdingportion 12b, and the engaging pieces 41e approach the inner wall surfaceof the through hole 12c. Additionally, the front end 31c of the fixingpin 31 comes into contact with the clip 13. Further, when the fixing pin31 is inserted through the through hole 12c against the biasing force ofthe clip 13, the clip 13 is elastically deformed in a radially outwarddirection of the fixing pin 31. Then, as shown in FIG. 12, when thefixing pin 31 is inserted to a location (a front-rear position) wherethe locking groove 31b corresponds to the clip 13, the clip 13 attemptsto enter the locking groove 31b by virtue of its own elastic restoringforce.

On the other hand, the claw portions 41d of the resin member 41 which isbiased to the front by the coil spring 35 has entered the interior ofthe locking groove 31b. Because of this, when the clip 13 enters theinterior of the locking groove 31b, the clip 13 forces itself betweenthe claw portions 41d and a front wall surface 31d of the locking groove31b while compressing the coil spring 35 to the rear. By the clip 13 soentering the locking groove 31b, the claw portions 41d are situated atthe rear of the clip 13 within the locking groove 31b. In the clip 13, aportion which is situated at the front of the through hole 12c issandwiched from front and rear by the claw portions 41d which are biasedto the front by the coil spring 35 and the front wall surface 31d of thelocking groove 31b, whereby the movement of the clip 13 is restricted.On the other hand, the fixing pin 31 is restricted from moving in thefront-rear direction by the clip 13 that has entered the locking groove31b. In this way, by the fixing pin 31 being locked on the metallic coreframe 12 by the clip 13, the fastening of each horn switch mechanism 15to the metallic core frame 12 and the mounting of the airbag device 20on the metallic core frame 12 can be executed. This locking structure oflocking the elements on the metallic core flame 12 by virtue of theelasticity of the clip 13 which is produced in association with theinsertion of the fixing pin 31 through the through hole 12c is alsoreferred to as a snap-in fitting structure.

In this assembled state, respective external surfaces of the engagingpieces 41e are brought into contact with the inner wall surface of thethrough hole 12c. Additionally, the claw portions 41d are slightlyspaced away to the front from a rear wall surface 31e of the lockinggroove 31b. In this way, the resin member 41 is interposed between theinner wall surface of the through hole 12c in the metallic core frame 12(the holding portion 12b) and the fixing pin 31.

Additionally, in the assembled state, the fixing pin 31 for each hornswitch mechanism 15 which is locked on the metallic core frame 12supports the airbag device 20 (the back holder 21) via the movable mountmember 32 so that the airbag device 20 can move back and forth (that is,the airbag device 20 moves towards and away from the metallic core frame12).

Here, the coil spring 35 which is interposed between a step portion 32fof the movable mount member 32 and the ring-like portion 41b of theresin member 41 has already been compressed before it is mounted on themetallic core frame 12. This coil spring 35 which is so compressedbiases the move mount member 32 to the rear which is the direction inwhich the movable mount member 32 moves away from the metallic coremember 12, whereby the contact terminal 34 is spaced away to the rearfrom the collar portion 31a of the fixing pin 31.

By being compressed further, the coil spring 35 permits the airbagdevice 20 to move towards the side of the metallic core frame 12.Namely, the coil spring 35 is compressed with a horn stroke ensured. Thehorn stroke means a traveling amount of the airbag device 20 towards themetallic core frame 12 which is necessary to move the contact terminal34 from a state in which the contact terminal 34 is spaced away from thecollar portion 31a of the fixing pin 31 (an off state of the horn switchmechanism 15: FIG. 12) to a state in which the contact terminal 34 comesinto contact with the collar portion 31a (an on state of the horn switchmechanism 15: FIG. 14). Additionally, a load with which the driverpresses against the airbag device 20 to put the horn switch mechanism 15in the on state is determined by the coil spring 35.

Incidentally, in the steering wheel 10, when in a normal state in whichthe airbag device 20 is not pressed to the front or no excessive load isapplied to the airbag device, as shown in FIG. 12, the contact terminal34 moves away to the rear from the fixed side contact portion (thecollar portion 31a of the fixing pin 31). Then, the electricallycommunicating state ensured between the contact terminal 34 and thefixing pin 31 is released, whereby the horn unit 40 is kept inoperative.As this occurs, the rearward biasing force of the coil spring 35 isapplied to the collar portion 31a of the fixing pin 31 which is lockedon the metallic core frame 12 by the clip 13 via the movable mountmember 32.

Additionally, as this occurs, the forward biasing force of the coilspring 35 is applied to the resin member through the ring-like portion41b, and the claw portions 41d of the resin member 41 which enter theinterior of the locking groove 31b of the fixing pin 31 presses the clip13 in the locking groove 31b to the front. By the clip 13 being sopressed, the clip 13 is sandwiched from front and rear by the front wallsurface 31d of the locking groove 31b and the claw portions 41d.

In contrast with this, when the airbag device 20 is pressed to the frontor the excessive load is applied to the airbag device 20, whereby theback holder 21 is moved to the front against the coil spring 35, themovable mount member 32 of at least one horn switch mechanism 15 ispressed via the back holder 21 against the biasing force of the coilspring 35 to thereby move to the side of the metallic core frame 12 (tothe front side). The cap member 33 and the contact terminal 34 also moveto the side of the metallic core frame 12 (to the front side) togetherwith the back holder 21 and the movable mount member 32. As thesituation in which the excessive load is applied, for example, asituation is considered in which the vehicle is being driven on a roughroad, vibrating the airbag device 20 largely.

Then, as shown in FIG. 14, when at least one of the three projectingcontact portions 34e is brought into contact with the collar portion 31aof the fixing pin 31, an electric communication is established betweenthe metallic core frame 12 which is connected the ground GND (earthed toa vehicle body) and the back holder 21 via the clip 13, the fixing pin31 and the contact terminal 34. By establishing the electriccommunication in this way, the horn switch mechanism 15 is closed, andthe horn unit 40 which is electrically connected to the back holder 21is activated (sounds for a warning).

In this way, in addition to the function as the fixed side contactportion, the fixing pin 31 exhibits not only the function to be lockedon the metallic core frame 12 (the holding portion 12b) but also thefunction to support the back holder 21 so as to move in the front-reardirection relative to the metallic core frame 12.

In addition, when the back holder 21 is moved to the front in the waydescribed above, the rearward biasing force of the coil spring 35 whichhas been applied to the collar portion 31a of the fixing pin 31 via themovable mount member 32 (the back holder 21) until then is lost. Becauseof this, the fixing pin 31 is allowed to swing on the portion where itis locked on the metallic core frame 12 by the clip 13 as a fulcrum. Asthis occurs, the rearward biasing force that has been applied to theclip 13 through the front wail surface 31d in the locking groove 31buntil then is released, whereby the clip 13 is allowed to move withinthe locking groove 31b.

On the other hand, in the airbag device 20, when in a normal state inwhich a front impact that is produced when the vehicle is involved in afrontal collision is not applied to the vehicle, no gas is injected fromthe gas injection portion 23x of the inflator 23, whereby the airbag iskept in the folded state.

Even when in the normal state, there is a situation in which verticaland horizontal vibrations are applied to the steering wheel 10 while thevehicle is being driven at high speeds or the engine is idling. Thesevibrations are transmitted to the airbag device 20 by way of themetallic core frame 12, the horn switch mechanisms 15 and the elasticmembers 42.

In response to the vibrations the airbag device 20 functions as thedamper mass of the dynamic damper and the elastic members 42 function asthe springs of the dynamic damper.

For example, when the steering wheel 10 vibrates vertically with apredetermined frequency, the elastic members 42 vibrate verticallytogether with the airbag device 20 with a resonant frequency which isthe same or close to the predetermined frequency while being elasticallydeformed (resonates), so as to absorb the vertical vibration energy ofthe steering wheel 10. By absorbing the vibration energy in the waydescribed above, the vertical vibration of the steering wheel 10 issuppressed (controlled).

Additionally, when the steering wheel 10 vibrates horizontally with apredetermined frequency, the elastic members 42 vibrate horizontallytogether with the airbag device 20 with a resonant frequency which isthe same or close to the predetermined frequency while being elasticallydeformed, so as to absorb the horizontal vibration energy of thesteering wheel 10. By absorbing the vibration energy in the waydescribed above, the horizontal vibration of the steering wheel 10 issuppressed (controlled).

In this way, according to the embodiment, the vibrations in either ofthe vertical and horizontal directions that are applied to the steeringwheel 10 are dampened (controlled).

The groove portion 42c formed on the front surface and the grooveportion 42d formed on the rear surface of the elastic member 42facilitate the elastic deformation of the elastic member 42. Because ofthis, when the steering wheel 10 vibrates, the elastic member 42 tendsto resonate easily together with the airbag device 20.

Here, when the steering wheel 10 vibrates, it is considered that it isthe portion between the engaging portion 42a and the movable mountmember 32 (the insertion hole 42b) that is mainly elastically deformedin the annular elastic member 42.

Because of this, in this embodiment in which the groove portions 42c,42d are formed between the engaging portion 42a and the movable mountmember 32 (the insertion hole 42b), the portion in relation to theelastic deformation tends to be deformed elastically more easily.

When impact is applied to the vehicle from the front as a result of afrontal collision, the driver tends to be inclined to the front byvirtue of inertia. On the other hand, in the airbag device 20, when theinflator 23 is activated in response to the impact, the inflation gas isinjected from the gas injection portion 23x. When this inflation gas issupplied to the airbag, the airbag is deployed to be inflated. As thepressure applied to the skin portion 24a of the pad portion 24 continuesto increase due to the deployment and inflation of the airbag, the skinportion 24a is ruptured at the thin portion 24c. Then, the airbagcontinues to be deployed and inflated towards the rear through anopening generated by the rapture. The airbag deployed and inflated ispresent in front of the driver who is falling to the front by the impactproduced by the frontal collision, the driver who is falling to thefront is restrained, whereby the driver is protected from failing to thefront.

(1) According to the embodiment that has been described in detailheretofore, the following advantages can be provided.

The side wall portion 33b of the cap member 33 in each horn switchmechanism 15 is made use of as the extended portion which is extended tothe front. The engaged portion 21j which extends to the rear is formedon the circumferential edge portion of the mounting hole 21e of the backholder 21. The engaging portion 42a is provided on the elastic member 42which is made up of the recess portion which is opened at the frontsurface of the elastic member 42. Then, the elastic member 42 is made tobe sandwiched from front and rear by the engaged portion 21j which isfitted in the engaging portion 42a and the side wall portion 33b (FIG.14).

Because of this, by performing the simple work of inserting the movablemount member 32 through the elastic member 42 and fitting the fittedportion 21j in the engaging portion 42a, the elastic member 42 can bemounted easily on the movable mount member 32 and the back holder 21 insuch a state that the elastic member 42 is restricted from moving in thedirection which follows the steering shaft 14 and from moving in thedirection perpendicular to the steering shaft 14. As a result, theairbag device 20 and the elastic members 42 can be made to vibrate asdesigned while facilitating the mounting work of the elastic members 42,thereby making it possible to exhibit the vibration control effect.

(2) The groove portions 42c, 42d are formed on the front surface and therear surface of the elastic member 42, respectively (FIG. 9).

Because of this, the elastic deformation of the elastic member 42 can befacilitated by these groove portions 42c, 42d, thereby making itpossible to obtain the suppressing (controlling) effect of thevibrations of the steering wheel 10 to a further extent.

(3) The groove portions 42c, 42d are formed between the engaging portion42a and the movable mount member 32 (the insertion hole 42b) (FIG. 9).

Because of this, the portion of the elastic member 42 which is involvedin the elastic deformation thereof can be deformed elastically further,the effect obtained under (2) above can be obtained more easily.

(4) In Patent Document 1 described before, it is considered that inorder to mount the elastic members in the mounting holes in the hardback holder (bracket), the back holder (bracket) is disposed inside amold as an insert so as to mold elastic members of a resin around themounting holes. As this occurs, however, the back holder (bracket) whichis disposed inside the mold occupies a wide space, and hence, the numberof elastic members that can be molded at one time is decreased, callingfor an increase in cost.

In this regard, in the embodiment, after the elastic member 42 isformed, the engaged portion 21j of the back holder 21 is fitted in theengaging portion 42a (FIGS. 8, 9). Because of this, in molding elasticmembers 42 of a resin, the back holder 21 does not have to be disposedinside a mold as an insert. No insert (back holder 21) is necessary whenmolding elastic members 42, and a large number of elastic members 42 canbe molded at one time accordingly, thereby making it possible to realizea reduction in cost.

It should be noted that the invention can be embodied into a differentembodiment which will be described below.

<As to Engaged Portion 21j>

An engaged portion 21j only has to extend to the rear from acircumferential edge portion of a mounting hole 21e in a back holder 21.Therefore, as has been described in the embodiment above, the engagedportion 21j may be formed integrally with the back holder 21 or may beformed separately from the back holder 21.

There may be provided an annular engaged portion 21j or an arc-likeengaged portion 21j. In the former case, the number of engaged portions21j is one, but in the latter case, the number of engaged portions 21jmay be one or more.

<As to Elastic Member 42>

An engaging portion 42a of an elastic member 42 only has to be made upof a recess portion which is opened at the front face of the elasticmember 42 and only has to be at least such as to enable the engagedportion 21j to be fitted therein. Thus, the shape and size of theengaging portion 42a may be altered as long as the conditions above aremet.

One of groove portions 42c, 42d may be omitted. Namely, the grooveportion may be provided only on one of a front surface and a rearsurface of the elastic member 42.

At least one of the groove portions 42c, 42d may be provided at aplurality of locations on the elastic member 42.

<As to Extended Portion>

A member which is different from the sick wall portion 33b of the capmember 33 may be used as an extended portion which is extended to thefront on a horn switch mechanism 15. For example, an extended portionmay be provided on a cap member 33 separately from a side wall portion33b. Also, the extended portion may be provided separately from the capmember 33.

<As to Support Member>

In place of the fixing pin 31, a replacement member which satisfies thefollowing conditions may be used as a support member.

Condition 1: The replacement member should be inserted through thethrough hole 12c to thereby be locked on the metallic core frame 12 bythe elastic member (the clip 13).

Condition 2: By being inserted through the back holder 21, thereplacement member should support the back holder 21 so as to move inthe front-rear direction relative to the metallic core frame 12.

Condition 3: The replacement member should have the pressure bearingportion (the collar portion 31a) which bears the rearward biasing forceby the biasing member (the coil spring 35) in a position on a rear sideof the back holder 21.

Condition 4: The replacement member should be formed of a metal havingconductivity, and the rear end face (the collar portion 31a) thereoffunctions as the fixed side contact portion.

<Others>

The damping system of the invention can be applied to steering wheels ofsteering systems of vehicles such as aircraft and ships, in addition tothe motor vehicles as described above. In this case, the motor vehiclesare not limited to private vehicles, but may be various types ofindustrial vehicles.

What is claimed is:
 1. A damping system for a steering wheel,comprising: a fixed member fixed to a steering shaft extending in afront-rear direction; an airbag device which comprises a back holderprovided at a front portion thereof and which is disposed on a rear sideof the fixed member; an elastic member mounted in a mounting hole formedin the back holder so as to penetrate therethrough in a front-to-reardirection; and a horn switch mechanism comprising: a support membersupported on the fixed member at a position on a front side of the backholder; and a slider disposed between the support member and the elasticmember so as to activate a horn unit by a forward movement of the sliderassociated with a pressing operation of the airbag device, wherein saiddamping system allows the airbag device to function as a damper mass ofa dynamic damper, and allows the elastic member to function as a springof the dynamic damper, wherein the horn switch mechanism furthercomprises an extended portion extending forwards, wherein the backholder comprises an engaged portion extending rearwards and formed at acircumferential edge portion of the mounting hole, wherein the elasticmember comprises an engaging portion comprising a recess portion openedin a front surface of the elastic member, wherein the elastic member issandwiched by the engaged portion fitted in the engaging portion and theextended portion in the front-rear direction, and wherein the elasticmember is formed, as a whole, of an elastic materiel of rubber orelastomer.
 2. The damping system for a steering wheel according to claim1, wherein the elastic member comprises a groove portion which is openedin at least one of the front surface and a rear surface of the elasticmember.
 3. The damping system for a steering wheel according to claim 2,wherein the groove portion is formed between the engaging portion andthe slider.
 4. A damping system for a steering wheel comprising: anairbag device that includes a pad portion having a surface and a backholder forming a bag accommodation space between the pad portion and theback holder; a plurality of pins each having a front end portion, a rearend portion, a shaft portion extending in a front-rear direction, and acollar portion provided at the rear end portion, wherein a diameter ofthe collar portion is set to be larger than a diameter of the shaftportion; a plurality of elastic members, each of which is formed, as awhole, of an elastic material of rubber or elastomer and is locatedbetween the back holder and an outer periphery of a corresponding one ofthe pins; a plurality of sliders, each of which moves forward associatedwith a pressing operation of the airbag device and is located betweenthe outer periphery of a corresponding one of the pins and thecorresponding elastic member; and a plurality of biasing members, eachof which applies a biasing force to urge the airbag device away from thesteering wheel and is located around the outer periphery of acorresponding one of the pins, wherein each pin is mounted on thesteering wheel at the front end portion using a snap-in fittingstructure and supports the airbag device at the rear end portion, eachpin includes a locking groove formed at the front end portion, thesteering wheel includes a plurality of through holes, each of whichpasses through the steering wheel in the front-rear direction, aplurality of clips are held on the steering wheel corresponding to thethrough holes, the snap-in fitting structure includes the locking grooveof each pin and one of the clips that is engaged with the lockinggroove, the back holder includes a plurality of mounting portions and aplurality of mounting holes, wherein each mounting hole passes through acorresponding one of the mounting portions in the front-rear direction,the shaft portion of each pin and the corresponding slider are insertedinto a corresponding one of the mounting holes, the back holder includesa plurality of engaged portions, each of the engaged portions extendsrearward from a circumferential edge portion of a corresponding one ofthe mounting holes, each elastic member contacts a corresponding one ofthe sliders and a corresponding one of the engaged portions andsuppresses vibrations transmitted between the back holder and thecorresponding pin, the damping system allows the airbag device tofunction as a damper mass of a dynamic damper and allows the elasticmembers to function as a spring of the dynamic damper, and each elasticmember includes a portion, which is disposed between the correspondingslider and the corresponding engaged portion and contacts the engagedportion, and an inner surface of an insertion hole contacting thecorresponding slider, wherein the portion of the elastic member extendsin a radial direction of the corresponding mounting hole, and is locatedrearward of the corresponding mounting portion.
 5. The damping systemfor a steering wheel according to claim 4, wherein a resin member islocated between the front end portion of each pin and an inner peripheryof a corresponding one of the through holes.
 6. The damping system for asteering wheel according to claim 5, wherein the steering wheel has aframe portion that includes a fixed member, the through holes areprovided in the fixed member, and each pin is directly mounted on thefixed member using the snap-in fitting structure.
 7. The damping systemfor a steering wheel according to claim 4, wherein the engaged portionsare integrally formed with the back holder.
 8. The damping system for asteering wheel according to claim 4, wherein each elastic memberincludes a front surface, a rear surface, a front groove portion that isopened in the front surface, and a rear groove portion that is opened inthe rear surface, and the portion of each elastic member includes a partof the elastic member between a bottom surface of the front grooveportion and a bottom surface of the rear groove portion.
 9. The dampingsystem for a steering wheel according to claim 4, wherein a frontsurface is provided on the elastic member, and a part of the frontsurface abuts the corresponding mounting portion which is spaced apartfrom the corresponding slider by the elastic member.
 10. A dampingsystem for a steering wheel comprising: an airbag device that includes apad portion having a surface and a back holder forming a bagaccommodation space between the pad portion and the back holder; aplurality of pins each having a front end portion, a rear end portion, ashaft portion extending in a front-rear direction, and a collar portionprovided at the rear end portion, wherein a diameter of the collarportion is set to be larger than a diameter of the shaft portion; aplurality of elastic members, each of which is formed, as a whole, of anelastic material of rubber or elastomer and is located between the backholder and an outer periphery of a corresponding one of the pins; aplurality of sliders, each of which moves forward associated with apressing operation of the airbag device and is located between the outerperiphery of a corresponding one of the pins and the correspondingelastic member; and a plurality of biasing members, each of whichapplies a biasing force to urge the airbag device away from the steeringwheel and is located around the outer periphery of a corresponding oneof the pins, wherein each pin is mounted on the steering wheel at thefront end portion using a snap-in fitting structure and supports theairbag device at the rear end portion, each pin includes a lockinggroove formed at the front end portion, the steering wheel includes aplurality of through holes, each of which passes through the steeringwheel in the front-rear direction, a plurality of clips are held on thesteering wheel corresponding to the through holes, the snap-in fittingstructure includes the locking groove of each pin and one of the clipsthat is engaged with the locking groove, the back holder includes aplurality of mounting portions and a plurality of mounting holes,wherein each mounting hole passes through a corresponding one of themounting portions in the front-rear direction, the shaft portion of eachpin and the corresponding slider are inserted into a corresponding oneof the mounting holes, the back holder includes a plurality of engagedportions, each of which extends rearward from a circumferential edgeportion of a corresponding one of the mounting holes, each elasticmember contacts a corresponding one of the sliders and a correspondingone of the engaged portions and suppresses vibrations transmittedbetween the back holder and the corresponding pin, the damping systemallows the airbag device to function as a damper mass of a dynamicdamper and allows the elastic members to function as a spring of thedynamic damper, and each elastic member includes a portion, which isdisposed between the corresponding slider and the corresponding engagedportion and contacts the engaged portion, and an inner surface of aninsertion hole contacting the corresponding slider, wherein the portionof the elastic member extends in a radial direction of the correspondingmounting hole, and the insertion hole extends forward of a rear surfaceof the corresponding mounting portion.
 11. The damping system for asteering wheel according to claim 10, wherein the engaged portions areintegrally formed with the back holder.
 12. A damping system for asteering wheel comprising: an airbag device that includes a pad portionhaving a surface and a back holder forming a bag accommodation spacebetween the pad portion and the back holder; a plurality of pins eachhaving a front end portion, a rear end portion, a shaft portionextending in a front-rear direction, and a collar portion provided atthe rear end portion, wherein a diameter of the collar portion is set tobe larger than a diameter of the shaft portion; a plurality of elasticmembers, each of which is formed, as a whole, of an elastic material ofrubber or elastomer and is located between the back holder and an outerperiphery of a corresponding one of the pins; a plurality of sliders,each of which moves forward associated with a pressing operation of theairbag device and is located between the outer periphery of acorresponding one of the pins and the corresponding elastic member; anda plurality of biasing members, each of which applies a biasing force tourge the airbag device away from the steering wheel and is locatedaround the outer periphery of a corresponding one of the pins, whereineach pin is mounted on the steering wheel at the front end portion usinga snap-in fitting structure and supports the airbag device at the rearend portion, each pin includes a locking groove formed at the front endportion, the steering wheel includes a plurality of through holes, eachof which passes through the steering wheel in the front-rear direction,a plurality of clips are held on the steering wheel corresponding to thethrough holes, the snap-in fitting structure includes the locking grooveof each pin and one of the clips that is engaged with the lockinggroove, the back holder includes a plurality of mounting portions and aplurality of mounting holes, wherein each mounting hole passes through acorresponding one of the mounting portions in the front-rear direction,the shaft portion of each pin and the corresponding slider are insertedinto a corresponding one of the mounting holes, each elastic member islocated on an outer side of a corresponding one of the sliders andsuppresses vibrations transmitted between the back holder and thecorresponding pin, the damping system allows the airbag device tofunction as a damper mass of a dynamic damper and allows the elasticmembers to function as a spring of the dynamic damper, and each elasticmember includes a portion, which is disposed between the correspondingmounting portion and the corresponding slider in a radial direction ofthe corresponding mounting hole, and an inner surface of an insertionhole contacting the corresponding slider, wherein the portion of theelastic member extends in the radial direction and is located rearwardof the corresponding mounting portion, wherein a front surface isprovided on the elastic member, and a part of the front surface abutsthe corresponding mounting portion which is spaced apart from thecorresponding slider by the elastic member.
 13. The damping system for asteering wheel according to claim 12, wherein each elastic memberfurther includes a rear surface, a front groove portion that is openedin the front surface, and a rear groove portion that is opened in therear surface, and the portion of each elastic member includes a part ofthe elastic member between a bottom surface of the front groove portionand a bottom surface of the rear groove portion.